Pressure actuated locking device

ABSTRACT

A pressure-sensitive locking device comprises a housing ( 2,20 ) having an opening therein, and an insertable member ( 1,21 ) adapted to be inserted into the opening whereupon it can enter into locking engagement with a locking member ( 4,36 ) in the housing. The locking member ( 4,36 ) is cooperable with pressure-sensitive means ( 7,28 ) in the housing to effect disengagement between the locking member ( 4,36 ) and the insertable member ( 1,21 ) upon a reduction of pressure.

FIELD OF THE INVENTION

This invention relates to a locking device, and more particularly to alocking device which is automatically engageable or disengageable upon achange in pressure.

BACKGROUND OF THE INVENTION

A particular application for such a locking device is as a security sealfor use on passenger aircraft. The device can be used to seal thecontainers used for the in-flight distribution of perishable andnon-perishable goods. The theft of goods from containers costs airlinesvast sums of money each year. Although containers are sealed when theyleave the warehouse, it is necessary for the seals to be easilyremovable by hand as it is quite impractical for cabin crews to carryspecial seal removal tools on the aircraft. We have found that theseproblems can be solved by a locking device which is pressure-sensitive;the device thus being actuated by the reduced pressure during flight.

SUMMARY OF THE INVENTION

The present invention thus provides a pressure-sensitive locking devicecomprising a housing having an opening therein, an insertable memberadapted to be inserted into the housing through the opening, and alocking member in the housing, the locking member being biased towardsengagement with the insertable member so that the locking member islockably engageable with the insertable member upon insertion of theinsertable member into the housing, and the locking member beingcooperable with pressure-sensitive means pressure-sensitive arrangementin the housing to effect disengagement of the locking member from theinsertable member upon a reduction of pressure.

In a preferred embodiment, the locking member is resiliently biasedtowards the insertable member when inserted in the housing so as to bein locking engagement therewith under normal atmospheric pressure. Whenthe pressure is reduced, for example when an aircraft achieves apredetermined altitude, the pressure-sensitive means effectsdisengagement of the locking member from the insertable member,whereupon the insertable member can be withdrawn from the housing.

The opening in the housing preferably communicates with a channel, andthe insertable member is preferably elongate and adapted to be slidinglyinserted lengthwise through the opening into the channel.

The locking device can serve both as a barrier seal and as an indicativeseal. The elongate member can be shaped so as to engage with a hasp orother securing device of an aircraft goods container. Alternatively, theelongate member can be U or J-shaped whereby the limbs can be insertedin two channels in the housing and lockable in one or both suchchannels, the device then being usable in the same way as a padlock. Thelocking device preferably includes an additional disposable lockingelement which engages with the elongate member in the locked position,and which has to be physically broken to permit withdrawal of theelongate member from the channel.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying drawings, in which:

FIG. 1 is a diagrammatic representation, partly in cross-section, of alocking device according to a first embodiment of the invention, thedevice being shown in the locked condition;

FIG. 2 is a view corresponding to FIG. 1 but with the device unlocked;

FIG. 3 is an exploded perspective view of a locking device according toa second embodiment of the invention;

FIG. 4 is an end view of a disposable locking element used in the secondembodiment;

FIG. 5 is a plan view of the second embodiment when ready to be locked;

FIG. 6 is a plan view of the second embodiment in the locked position,and partly cutaway to show internal details;

FIG. 7 is a view of a combined capsule and locking member used in thesecond embodiment;

FIG. 8 is a side view corresponding to FIG. 7;

FIG. 9 is a partial end view corresponding to FIGS. 7 and 8;

FIG. 10 is a part-sectional side view showing the operation of thecombined capsule and locking member of the second embodiment in thelocked condition;

FIG. 11 corresponds to FIG. 10 and shows the device unlocked by areduction in air pressure;

FIG. 12 corresponds to FIGS. 10 and 11 and shows the operation of asecondary locking member to prevent unauthorised or accidental “shock”opening;

FIGS. 13 and 14 are diagrammatic plan views showing a modification ofthe second embodiment; and

FIGS. 15 and 16 are sectional views corresponding respectively to FIGS.13 and 14.

DETAILED DESCRIPTION OF THE INVENTION

Referring first to FIGS. 1 and 2, there is shown a housing 2 with achannel 9 defined therein. An elongate member in the form of a bar 1 ofcylindrical section is able to slide within the channel. The bar 1 has atapered head and immediately behind this a groove 3. A locking member 4is provided within the housing and is rotatable about an axis 10. Oneend of the locking member has an enlarged head shaped so as to engagewith the groove 3 of the bar 1. An opposite end of the locking member 4is engaged with one end of a helical spring 8, the other end of which ismounted in the housing 2. The spring 8 resiliently biases the lockingmember 4 into locking engagement with the groove 3 of the bar 1. Whenthe bar 1 is initially inserted into the channel 9, the tapered head ofthe bar slides past a sloping surface of the head of the locking member4, thereby deflecting the locking member against its spring bias, andthen the locking member snaps into engagement with the groove 3. Thelocking engagement between the locking member 4 and the groove 3prevents withdrawal of the bar 1 from the channel 9.

Also provided within the housing is a pressure-sensitive means in theform of a capsule 7 which communicates with a tube 6 but is otherwiseair-tight. The capsule 7 has concertina-like flexible side walls topermit expansion and contraction. An elongated sliding element 5 withrounded ends is provided in a transverse channel 11 which adjoins thechannel 9. Before insertion of the bar 1, one end of the sliding element11 projects slightly into the channel 9. As the bar 1 is inserted, itdeflects the sliding element 5 to one side so that it slides furtherinto the transverse channel 11. This causes the opposite end of thesliding element 5 to press against the side of the tube 6, which is offlexible material. The tube 6 is thereby sealed at this point, with theresult that the capsule 7 is completely air-tight.

As the pressure is reduced, for example, as an aircraft increasesaltitude, the pressure of the air enclosed within the capsule 7 becomesgreater than that of the surrounding air, with the result that thecapsule expands, as shown in FIG. 2. An end of the capsule 7 abutsagainst a rounded contact point on the locking piece 4, intermediate theaxis 10 and contact point of the spring 8. Expansion of the capsule 7,as shown in FIG. 2, thus causes the locking piece 4 to pivot about theaxis 10, whereby the head of the locking piece 4 becomes disengaged fromthe groove 3 in the bar 1. The bar 1 can then be freely withdrawn fromthe channel 9. Once the bar 1 has been withdrawn, the sliding element 5ceases to be pressed against the tube 6, and the natural resilience ofthe tube 6 pushes the sliding element 5 back towards the channel 9. Aircan therefore pass from within the capsule 7 and out through the tube 6,thereby equalising the pressures inside and outside the capsule 7. Thespring 8 will then cause pivoting of the locking piece 4 about the axis10, so that the head of the locking piece 4 once more projects into thechannel 9. If the bar 1 is then reinserted into the channel 9, it willagain engage with the head of the locking piece 4 to effect locking.Once this position has been reached, and without any further reductionin pressure, unlocking of the device can only be achieved by destructionof parts thereof, for example by cutting the bar 1. If desired, aspecial tool could be designed to disengage the locking piece 4 from thebar 1, although such an arrangement would be inherently less secure.

The locking device described above is typically used to seal a goodscontainer, for example a drinks trolley, for use on an aircraft. Thetrolley is filled at the warehouse and then locked with the lockingdevice. If the trolley is to be inspected by authorised personnel whilestill on the ground, the locking device is opened by cutting the bar,and the trolley is then locked with a new locking device. The lockingdevice can thus only be opened on the ground by destroying at least partof it, and thus any interference with the trolley is readily apparent toan inspector. Once on the aircraft, above a designated altitude, thelocking device is automatically unlocked by the reduced pressure. Thetrolley can then be used in the normal way, and after use it can berelocked with the same locking device. Thereafter, the locking devicecan again only be unlocked by destruction of at least part of it, whichwould be done by authorised personnel. Again, any unauthorisedinterference would be readily apparent to an inspector.

Referring now to FIGS. 3 to 12, a second embodiment of the invention isdescribed. The locking device shown includes a housing 20, an insertablemember in the form of a flat bar 21 and a disposable locking element 22.The housing has a hinged guide member 23, pivoted to an end portion 24of the housing. The guide member 23 is able to pivot between an openposition (FIG. 5) and a closed position (FIG. 6). The guide member 23has an opening 25 for receiving the bar 21, and in the closed positionthe opening 25, which extends through the guide member, is in registerwith openings at opposing ends of the main body of the housing 20, so asto effectively form a channel through the housing.

The bar 21 is J-shaped. An end portion of the longer limb can bepre-placed in the opening 25 of the guide member 23, with the guidemember in the open position as shown in FIG. 5. In order to effectlocking, as described in more detail below, the guide member 23 is thenrotated to the closed position (FIG. 6) and the longer limb of the bar21 is then fully inserted in the channel of the housing 20, the endportion of the longer limb projecting slightly from the other side ofthe housing (FIG. 6). The shorter limb of the bar 21 is received in anopening 26 in a side wall of the housing, and in the locked positiontravels to a short extent through the opening into the interior of thehousing (FIG. 6). The fit of the end of the longer limb of the bar 21 inthe opening 25 is sufficiently close that the bar 21 can be held by theguide member 23, as shown in FIG. 5, but does not impede furtherinsertion of the bar 21 through the opening 25 until the bar reaches thelocked position, as shown in FIG. 6.

Inside the housing 20 is a locking member 27 which incorporates apressure-sensitive device in the form of a sealed capsule 28. Thecapsule 28 is in the form of a shallow cylindrical cup, one end of whichis sealed by an elastomeric membrane 29. The cup and the membrane definea closed space. A short extension piece 30 to one side of the capsuleterminates in a transverse hinge member 31 which cooperates with a hingesupport 32 inside and at one end of the housing 20. Extending from theopposite side of the capsule 28, but slightly offset from the extensionpiece 30, is an arm 33. On the underside of the arm, close to thecapsule 28, there is formed a cylindrical cup 34 for receiving an end ofa helical spring 35, the other end of the spring being mounted on aninternal wall of the housing. By virtue of the hinge 31 and the spring35, the arm 33 of the locking member is biased away from the internalwall of the housing on which the spring 35 is mounted. Also on theunderside of the arm 33, but closer to its free end, there is anintegral locking piece 36 in the form of a ridge having a sloping ramp37 at one side (FIG. 9).

The bar 21 has a rectangular slot 38 towards the end of its longer limb.As the bar 21 is inserted into the housing, the leading edge of itslonger limb passes under the arm 33 of the locking member. The leadingedge first strikes the ramp 37 of the locking piece 36, and rides up theramp, thereby pressing the arm 33 against the bias of the spring 35. Onfurther insertion, the locking piece 36 becomes level with the slot 38in the bar 21, and at this point the spring 35 causes the arm 33 withits integral locking piece 36 to snap into engagement with the slot 38.Attempted withdrawal of the bar 21 is prevented by engagement betweenthe end of the locking piece 36, opposite to the ramp 37, with thetrailing end (on extraction) of the slot 38.

In this position, the bar 21 is securely locked in the housing 20. Withthis arrangement, there is a risk that a sharp blow to one side of thehousing, closest to the underside of the arm 33, could momentarilydeflect the arm against the spring 35, which would permit the bar 21 tobe withdrawn (referred to herein as “shock opening”). Such a blow couldbe inflicted deliberately in an attempt to interfere with the lockingdevice, or by accident. In order to overcome this problem, there isprovided a secondary locking member 39 (FIGS. 10 to 12). The secondarylocking member 39 is shaped similarly to the locking member 27 exceptthat it does not have the capsule 28. The secondary locking member 39has at one end a hinge member 40 which is mounted inside the housingclose to the hinge member 31 of the locking member 27. Close to itsopposite end, there is an integral upstanding locking piece 41, similarto the locking piece 36 but without a ramp. As shown in FIG. 10, thesecondary locking member 39 normally lies alongside an internal wall ofthe housing, with the locking piece 41 close to but not actually engagedwith the slot 38 of the bar 21. In this position, if a sharp blow isapplied to the housing wall adjacent the secondary locking member, thelocking member 27 may be momentarily deflected out of engagement withthe slot 38, as shown in FIG. 12. However, such a blow will deflect thesecondary locking member 39 in the same direction, and this will be intolocking engagement between the locking piece 41 and the slot 38. Theslot 38 is designed to be sufficiently wide that both locking pieces 36and 41, which are offset from each other, can be accommodated. When theeffect of the sharp blow has subsided, the spring 35 returns the lockingmember 27 and locking piece 36 into engagement with the slot 38 of thebar 21, and the arrangement is again as shown in FIG. 10.

When the locking device is in the locked position (FIG. 10) apredetermined reduction in ambient pressure will cause it to beunlocked. When the ambient pressure is reduced, the pressure of the airenclosed in the sealed capsule 27 causes the elastomeric membrane 29 toexpand outwardly. This membrane abuts against the surface of thesecondary locking member 39, which in turn abuts against the internalsurface of the housing. The result is that the locking member 27, byvirtue of its hinge 31, is pressed against the bias of the spring 35,and the locking piece 36 is raised out of engagement with the slot 38,as shown in FIG. 11. The locking device is then unlocked, and the bar 21can be withdrawn. The elastomeric grade of the membrane 29 can beadapted to provide locking devices which will be unlocked over a rangeof predetermined pressure changes.

The locking device includes a supplementary security seal in the form ofa disposable locking element 22 (FIGS. 3 and 4). The disposable lockingelement 22 includes a head part 42 in the form of a flat tab, andupstanding on one side thereof a plug part 43 and a locking post 44. Thedisposable locking element 22 cooperates with the guide member 23 (whichis part of the housing 20) and the bar 21 in the following manner.

The bar 21 has a circular hole 45 in its longer limb spaced from thetrailing end (on insertion) of the slot 38. The guide member 23 has acorresponding through hole 46 whereby, when the bar 21 is locked in thehousing 20, the holes 45 and 46 are in register and can receive thelocking post 44 of the disposable locking element 22. The guide member23 has a hollow interior, with an opening 47 spaced to one side of thehole 46. The plug part 43 of the disposable locking element is in theform of a resilient barb. The plug part 43 passes through the opening 47as the locking post 44 is inserted through the holes 46 and 45. As theplug part 43 passes through the opening 47, the barb is resilientlydeflected to one side, but as soon as it is inside the guide member 23,the barb resiliently returns to its original dimensions, and resistswithdrawal. In this position, the bar 21, as well as being locked by thelocking member 27 inside the housing, is additionally locked by thelocking post 44. Thus, even when a reduction in pressure has caused thelocking member 27 to disengage from the bar 21, the disposable lockingelement 22 must additionally be released in order to withdraw the bar21.

The head part 42 incorporates a tear line which separates the parts ofthe head part respectively attached to the plug part 43 and the lockingpost 44. Thus, by manual manipulation, which is assisted by a pull tab48, the disposable locking element can be split into two parts. Thelocking post 44 can then be freely withdrawn, permitting release of thebar 21. The plug part 43 remains inside the guide member 23 but theguide member 23 can now be freely rotated to the open position, therebyreleasing the plug part. The disposable locking element 22 can be markedfor security purposes, such as with a serial number or bar code. Ifdesired, the locking device can be relocked using a new disposablelocking element.

FIGS. 13 to 16 illustrate a modification of the second embodiment of theinvention (FIGS. 3 to 12). Instead of the secondary locking member 39(which is absent in FIGS. 13 to 16), shock opening is prevented bymodifying an internal chamber 49 in the housing and allowing a loose fitof the hinge 31. The loose fit permits a small amount of sidewaysmovement of the arm 33, whereby the bar 21 can be pushed slightly beyondits normal locking position (FIGS. 13 and 15) to an extended position(FIGS. 14 and 16). The effect of this can be seen by comparing FIG. 15,which is a section on the line XV—XV of FIG. 13, with FIG. 16, which isa similar section corresponding to FIG. 14. The chamber 49 is providedwith a step 50 near the point of entry of the bar 21. The step 50 isdimensioned such that the thickness of the arm 33 can just fit betweenthe step 50 and the bar 21. Thus, in the normal locking position shownin FIGS. 13 and 15, the step 50 prevents shock opening. Shock openingcan only be achieved if the bar 21 is pulled away from the housingsimultaneously with applying the shock, and in this position the step 50prevents movement of the arm 33 to take the locking piece 36 out ofengagement with the bar 21.

When a fall in pressure permits normal opening (in the manner alreadydescribed), the disposable locking element 22 is first extracted. Thebar 21 can then be pushed into the extended position (FIGS. 14 and 16),where the holes 45 and 46 are now slightly out of register. The arm 33is now moved off the step 50. The spring 35 will cause it to remain inengagement with the bar 21 (as shown in FIGS. 14 and 16). However, ifthe pressure has fallen sufficiently, the expansion of the capsule 28will cause the arm 33 to move out of engagement with the bar 21. The bar21 can then be pulled out of the housing as described above.

There may be a need to inspect a container locked by the locking devicewhile still on the ground. In this case, an authorised official willbreak the disposable locking element 22 and cut the bar 21 in its longerlimb, on the trailing side (relative to insertion) of the hole 45. Theleading end of the longer limb, which projects from the other side ofthe housing, can then be pulled, and the residual part of the bar 21withdrawn from the housing. This is possible because the ramp 37 of thelocking piece 36 will cooperate with the trailing end of the slot 38,whereby the locking member 27 is moved out of engagement with theresidual part of the bar 21. The device is then relocked with a new bar21 and new disposable locking element 22.

It is sometimes desirable for containers on aircraft to be openablewhile the aircraft is still on the ground, for example if there is aflight delay. This can be accommodated according to the presentinvention by modifying some locking devices so that the slot 38 isabsent in the bar 21. The device is then not locked by thepressure-sensitive locking member 27, but is only locked by thedisposable locking element 22. In a typical situation, a limited numberof containers of the aircraft would be locked in this way, the remainingcontainers being locked in the full pressure-sensitive manner asdescribed above.

A container on an aircraft may be locked by the device according to theinvention by cooperation between the bar 21 and a hasp or other securingdevice on the container. Alternatively, a cable may be provided withloops at its end. The cable is then used to secure a container door inthe closed position and the loops are held by the bar 21 which acts inthe manner of a padlock.

What is claimed is:
 1. A pressure-sensitive locking device comprising ahousing having an opening in an external surface which communicates witha channel in the housing, an insertable elongate member having a leadingportion and adapted to be slidingly inserted through the opening so thatthe leading portion is within the channel and the trailing portionremains outside the housing, and a locking member in the housing, thelocking member being biased towards engagement with the leading portionof the insertable member so that the locking member is lockablyengageable with the leading portion of the insertable member uponinsertion of the insertable member into the housing, and the lockingmember being cooperable with a pressure-sensitive device in the housingto effect disengagement of the locking member from the insertablemember, said pressure-sensitive device being actuatable upon a reductionof ambient pressure, whereupon the insertable member can be withdrawnfrom the housing.
 2. A locking device according to claim 1, in which thelocking member is pivotable.
 3. A locking device comprising: a housinghaving an opening which communicates with a channel in the housing, aninsertable elongate member adapted to be slidingly inserted through theopening and into the channel, and a locking member in the housing, thelocking member being biased towards engagement with the insertablemember so that the locking member is lockably engageable with theinsertable member upon insertion of the insertable member into thehousing, the locking member being cooperable with a pressure-sensitivearrangement in the housing to effect disengagement of the locking memberfrom the insertable member the pressure-sensitive arrangement beingactuatable upon a reduction of ambient pressure, and wherein thepressure-sensitive arrangement comprises an expandable sealed capsule inabutment with a surface of the locking member, whereby expansion of thecapsule causes movement of the locking member out of engagement with theinsertable member.
 4. A locking device according to claim 3, includingmeans for permitting air to flow freely in or out of the capsule whenthe insertable member is totally or partially withdrawn from thehousing.
 5. A locking device according to claim 1, in which thepressure-sensitive device comprises a sealed capsule incorporated in thelocking member, the capsule having an expandable surface in abutmentwith a surface in the housing, whereby a reduction in pressure causesexpansion of the expandable surface and consequent movement of thelocking member out of engagement with the insertable member.
 6. Alocking device comprising: a housing having an opening whichcommunicates with a channel in the housing, an insertable elongatemember adapted to be slidingly inserted through the opening and into thechannel, and a locking member in the housing, the locking member beingbiased towards engagement with the insertable member so that the lockingmember is lockably engageable with the insertable member upon insertionof the insertable member into the housing, the locking member beingcooperable with a pressure-sensitive arrangement in the housing toeffect disengagement of the locking member from the insertable member,the pressure-sensitive arrangement being actuatable upon a reduction ofambient pressure, and further comprising a secondary locking memberadapted to lockably engage with the insertable member when an appliedshock displaces the locking member out of engagement with the insertablemember.
 7. A locking device comprising: a housing having an openingwhich communicates with a channel in the housing, an insertable elongatemember adapted to be slidingly inserted through the opening and into thechannel, and a locking member in the housing, the locking member beingbiased towards engagement with the insertable member so that the lockingmember is lockably engageable with the insertable member upon insertionof the insertable member into the housing, the locking member beingcooperable with a pressure-sensitive arrangement in the housing toeffect disengagement of the locking member from the insertable member,the pressure-sensitive arrangement being actuatable upon a reduction ofambient pressure, and wherein a step inside the housing is in abutmentwith the locking member so as to prevent the locking member becomingdisengaged from the insertable member on application of a shock, andwherein further insertion of the insertable member into the housingmoves the locking member out of abutment with the step, whereupondisengagement of the locking member from the insertable member becomespossible.
 8. A locking device comprising: a housing having an openingwhich communicates with a channel in the housing, an insertable elongatemember adapted to be slidingly inserted through the opening and into thechannel, and a locking member in the housing, the locking member beingbiased towards engagement with the insertable member so that the lockingmember is lockably engageable with the insertable member upon insertionof the insertable member into the housing, the locking member beingcooperable with a pressure-sensitive arrangement in the housing toeffect disengagement of the locking member from the insertable member,the pressure-sensitive arrangement being actuatable upon a reduction ofambient pressure, and further comprising a disposable locking elementadapted to engage with one of the insertable member and the housing whenthe insertable member is in locking engagement with the locking member,whereupon breakage of part of the disposable locking element permitsdisengagement thereof from the one of the insertable member and from thehousing.
 9. A locking device to claim 8, in which the disposable lockingelement is adapted to lockably engage with one of the insertable memberand the housing, whereby withdrawal of the insertable member from thehousing is prevented even when the locking member is disengaged from theinsertable member.
 10. A locking device according to claim 8, in whichthe disposable locking element is formed of a plastic material andincludes a head part and a plug part, the plug part being resilientlydeformable so as to permit engagement with but resist disengagement fromthe one of the housing and the insertable member, and the head partincluding a tear line whereby manual manipulation of the head part willpermit separation thereof from the plug part with resultantdisengagement from the one of the housing and the insertable member.